Assets on the Fed’s balance sheet expanded to around $2.367 trillion in the latest week. But all the additions came from new Treasury purchases — some $18 billion just in the week ended Dec. 15. All other holdings were flat to lower. The Fed announced in November that it will purchase an additional $600 billion of Treasurys over the next eight months in addition to previously announced purchases with money reinvested from its MBS portfolio. Since the announcement, the Fed has purchased nearly $130 billion in Treasurys, while its MBS portfolio has declined by $42 trillion.

Though the overall size of the balance sheet is set to jump, the makeup is moving back toward the long-term trend. The MBS and agency debt holdings have steadily declined as loans are paid off or mature. The Fed still holds more assets in MBS — over $1 trillion — than any other portfolio, including Treasurys. Though at around $970 billion, Treasurys are catching up.

Meanwhile, other assets were also declining. The Term Asset-Backed Securities Loan Facility, or TALF, ended in March, and is falling as the last loans made through the program mature. Liquidity swaps with foreign central banks have fallen back to the millions of dollars after jumping in the spring in response to European sovereign debt concerns. Direct-bank lending was essentially flat, remaining at precrisis levels.

In an effort to track the Fed’s actions, Real Time Economics has created an interactive graphic that will mark the expansion of the central bank’s balance sheet. The chart will be updated as often as possible with the latest data released by the Fed.